USSPRD - Reads an IUE ULDA spectrum as produced by USSP

Syntax:

USSPRD filename[.typ] [epsmin]

Description:

Reads data from the IUE `Uniform' Low Dispersion Atlas, ULDA, which have been output using the USSP (see SUN/20). The filename extension defaults to `.ULD'. This command cannot read NDFs. Each point in the USSP spectrum has an associated error index, called epsilon, with the following meanings:

• 100 : No special conditions
• -200 : Extrapolated at upper end of ITF
• -220 : Microphonic noise
• -250 : Filtered bright spot
• -300 : Unfiltered bright spot
• -800 : Reseau in extracted spectral region
• -1600 : Saturated
• -3200 : Not photometrically corrected

The epsilons are not necessarily reliable indicators of data quality. DIPSO rejects points on input if they are flagged with an epsilon less than or equal to `epsmin' (which defaults to -251), leaving the spectrum in the current arrays. It is forbidden to set epsmin less than or equal -1600, since this would result in totally unflagged, certainly bad, data being acquired.

If epsmin is given a value greater than zero, then all datapoints are read into the next available stack entry, and the epsilon array into the subsequent stack entry. More subtle doctoring of the data is then possible, using USSPCLIP (q.v.). However, it is recommended that the default epsmin be accepted unless you really know what you're doing, and have good reasons to choose a different value.